Final answer:
A symbolic event marking the transition from childhood to adulthood is called a rite of passage, which consists of three stages: separation, transition, and incorporation.
Step-by-step explanation:
The term used to refer to a symbolic event or ritual that marks the transition from childhood to adulthood is called a rite of passage. Rites of passage are significant social ceremonies that represent the transition of an individual from one status to another, emphasizing changes at significant points in life, such as birth, puberty, marriage, and death. Arnold van Gennep, the anthropologist who first identified these rites, outlined three key stages in these rituals: separation, transition (or liminality), and incorporation. During the transition phase, the individual is in a state of 'betwixt and between', being neither in their previous status nor in the new one fully, making this the most crucial and transformative stage of the process.